Hadoop Data Nodes Do Not Appear In Web Interface

When accessing the Hadoop web interface (e.g. http://<ANALYTICS>:50070), the HDFS data nodes do not appear except any running on the Name Node.

Hadoop relies on the slaves and core-site.xml files to manage instances in its environment. Both of these files are located in /opt/interset/hadoop/etc/hadoop, and must be copied to this directory on all remote Hadoop installations (e.g. journal nodes, data nodes, secondary name node).

The slaves file contains the hostnames of all data nodes in the environment. These values should be listed 1 per line, and should correspond with the entries in the /etc/hosts file*.

The core-site.xml file dictates where the Name Node is located, in the fs.default.name parameter. Likewise, this should correspond with an entry in the /etc/hosts file.

If these files have been copied to all servers, also ensure that they are owned by the proper user (interset) and have appropriate permissions (minimum 400/r--).

*Apache best practices note that hostnames used in its configuration files should be hard coded in the systems' /etc/hosts file. More information on this can be found @ https://wiki.apache.org/hadoop/UnknownHost.